Actinomyces viscosus, a prominent member of the supragingival plaque microbiota, has been implicated in the etiology of gingivitis and periodontitis. Previous research has indicated that this organism possesses the armamentarium to activate host immune and non-immune systems which could be responsible for the hard and soft tissue destruction characteristic of these diseases. For example, several laboratories have confirmed the observation that A. viscosus produces cell-associated and cell-free mitogens capable of polyclonal B-cell activation and non-specific immunoglobulin synthesis. Since these mitogens have not been purified, little is known of their composition or mode of action. The studies detailed below will extend our knowledge of the basic biology and chemical composition of surface components of A. viscosus following enzymic digestion of the cell wall under protoplasting conditions. A potent murine splenocyte mitogen will be purified from whole cells and compared to one "shed" during growth. Both active components will be chemically characterized and the responding cell type identified. Chemostate cultures will be utilized to evaluate the influence of growth rate, pH, and degree of aerobiosis in steady-state cultures and during transients of glucose. The interactions between A. viscosus and adherent macrophages will be characterized, including possible persistence of cell wall components within phagocytic cells utilizing mutants in which the cross-bridge in the peptidoglycan is specifically labelled with 14C-ornithine. The proposed research will extend our specific knowledge of the role A. viscosus may play in inflammatory oral diseases and expand our general knowledge of the biology and physiology of plaque bacteria.